Manufacture of steel.



UN TED STATES HORACE W. LASH, OF CLEVELAND, OHIO, ASSIGNOR TO THE GARRETT- CROMVVELL ENGINEERING COMPANY, OF C PORATION OF OHIO.

PATENT OFFICE.

MANUFACTURE OF STEEL.

To all whom it may concern:

Be it known that I, HORACE W. LAsH, a citi- Zen of the United States, residing in Cleveland, in the county of (,uyahoga and State of Ohio, have invented certain new and useful Improvements in the Manufacture of Steel, of which the following is a full and true description.

My invention relates to the manufacture of steel from pig-iron, including thereby the molten iron drawn from the blast-furnace, by a new process, whereby the conversion of the pig metal is speedily and economically accomplished.

By my process steel may be produced from the pig-iron obtained from non-bessemer ores of the low-grade variety found in Alabama, Northern New York, and in Nova Scotia, which ores, as is well known, yield a pig-iron high in silicon and phosphorus and similar metalloids whiclr render open-hearth refining practically impossible under the present commercial conditions.

The usual method of producing Bessemer steel is by taking molten metal direct froma blast-furnace or from a cupola, running the molten metal obtained from either source into a Bessemer converter, and blowing air through the metal, whereby the manganese, silicon, and carbon are oxidized and removed therefrom. The bessemerized metal thus produced has sometimes been transferred to an open-hearth furnace for further treatment, a procedure which is expensive by reason of the fact that it becomes necessary to add carbon to the bath in the open-hearth furnace in order that the bath may be maintained fluid while beingsubjected to the dephosphorizing treatment. This transfer process just described involves the passage through the Bessemer converter of all of the metal run into the open hearth, and thereby becomes exceedingly expensive, owing to the doubling of the ordinary charges for labor, carriage, fuel, 850.

Another old method of manufacturing openhearth steel has been to melt pig-iron with scrap as a dilutent in the open-hearth furnace and to remove the manganese, silicon, and carbon by the addition of iron ore. This process is now rapidly becoming an impossibility, owing to the rising price of scrap, and it is therefore obviously desirable to manufacture open hearth steel from pig-iron alone. In

Specification of Letters Patent. Application filed October 24, 1902. Serial No. 128,634.

Patented Nov. 28, 1905.

order to do this entirely in the open hearth, a great quantity of iron ore is required to remove the carbon and the silicon from the bath, and thisis distinctlyobjectionable, since a highly silicious slag is produced which renders the removal of phosphorus difficult.

From the foregoing it will be seen that it is necessary in producing open-hearth steel to so conduct the process of refining that the open-hearth bath shall have therein a sufficient quantity of carbon to admit of the bath being retained molten until the dephosphorization shall have been completed and yet contain so little silicon that the quantity of basic additions usually required will be lessened and there will be formed comparatively little silicious slag.

My new process is directed to producing open-hearth steel from pig-iron alone under the conditions just recited, proceeding in such manner that the bath shall be furnished with sufficient carbon to prevent the product under treatment too nearly approaching metallic iron, as well as rendering unnecessary the addition of carbon-bearing material to the bath, while the oxidation of the silicon present will result in the formation of avery small quantity of slag.

In carrying out my process I divide the pigiron charge and treat the larger portion in the ordinary Bessemer converter, which, as is well known in the art, is acid-lined and adapted for the removal of such metalloids as manganese, silicon, and 'carbon. The smaller portionof the charge is run from the blast -furnace or other source directly into a basic-lined open-hearth furnace and held therein. That portion of the charge which is run into the Bessemer converter is blown until the manganese, silicon, and carbon are removed to the extent usual in the Bessemer process, which, while not resulting in a metal absolutely free from these metalloids, gives a product in which they are negligible quantities for all practical purposes. This bessemerized metal is then charged into the bath of crude or unrefined metal in the basic-lined open-hearth furnace, whereupon a violent chemical reaction takes place due to the mingling of the refined and unrefined masses, the former being vgsaally at a considerably higher temperature, and to the action of the oxygen carried into the bath by the LEVELAND, OHIO, A COR- converter charge upon the carbon and silicon of the crude or unrefined metal, the dephosphorization of the mixture being then rapidly accomplished with the formation of little slag. The treatment of the larger portion of the charge in the Bessemer converter before transference to the open-hearth furnace removes such a quantity of silicon that the total amount of the final charge, including the portion contained in the crude metal and the trace coming in with the bessemerized metal, is insufficient to produce an objectionable amount of slag. The total carbon of the combined charge, including that of the crude metal and the trace left in the bessemerized metal, is sufiicientto allow the dephosphorizing of the mass to be carried on without decreasing the amount of carbon too much.

1 have found that the best proportions to use for the two divisions of the charge are seventy-five per cent. for the part to be subjected to the treatment in the Bessemer converter and twenty-five per cent. for the part to be run directly into the basic-lined open hearth. That portion of the charge which is partially refined before being supplied to the open hearth is for economic reasons treated in successive quantities in a Bessemer converter, wherein the manganese, silicon, and carbon are removed and the metal is charged with oxygen, and as rapidly as converted the bessemerized metal is charged into the bath of unrefined metal.

What I claim is 1. The process ofmanufacturing steel from iron containing silicon and phosphorus which comprises runninga portion of the final charge of the crude metal into a basic-lined open hearth, blowing another portion of the final charge in an acid-lined converter until practically all the silicon has been removed and transferring the desiliconized metal to the open hearth while the total carbon of the combined charge is suflicient to allow the dephosphorization of the bath Without carboniferous additions.

2. The process of manufacturing steel from iron containing silicon and phosphorus, the silicon being present in sufficient quantity to form, upon oxidation in the open hearth, a slag materially interfering with the removal of the phosphorus which comprises dividing the charge into separate portions, running one portion into a basic-lined open hearth, running another portion into an acid-lined converter and blowing the latter to the point of practical desiliconization and transferring the desiliconized metal to the open hearth, whereby the total silicon of the final charge is reduced so that the slag formed is materially lessened, thereby facilitating the removal of the phosphorus.

3. The processgf.manufacturing steel from iron containing substantial percentages of silicon and a metalloid incapable of practical removal by acid treatment, which comprises introducing into a basic-lined open hearth a quantity of such crude iron as a portion of the final charge, blowing another portion of the final charge in an acid-lined converter until practically desiliconized and transferring the desiliconized metal to the basic-lined open hearth containing the crude metal while the total carbon of the final charge is sulficient to admit of the removal of the said metalloid incapable of removal by acid treatment.

4. The process of manufacturingsteel from crude iron containingphosphorus which comprises dividing the charge into separate portions, running one portion directly into a basiclined open-hearth furnace, running another portion into an acid-lined converter, oxidizing the converter charge and transferring the same to the open hearth, the proportions of the separate portions being so made that the carbon contents of the final openhearth charge will be suflicient, after oxidation by the oxygen carried into the bath by the converter charge, to permitdephosphorization without the addition of carbon-bearing material.

5. The process of manufacturing steel from pig-iron which comprises dividing the charge into separate portions, running one portion directly into a basic-lined open hearth, running another portion into an acid-lined converter, oxidizing the converter charge, transferring the latter into the open hearth and dephosphorizing the resultant bath, the proportions of the initial unrefined portion of the charge and the subsequent oxidized addition being such as to afford oxidation of silicon and carbon contained in the unrefined metal by the oxygen carried by the said addition and to admit of dephosphorization without carboniferous additions.

6. The process of manufacturing steel from pig-iron which comprises dividing the charge into separate portions, running one portion into a basic-lined open hearth, running other portions successively into an acid-lined converter, oxidizing the converter charges, running said charges consecutively at intervals into the open hearth and dephosphorizing the resultant bath, the proportions of the initial unrefined portion of the charge and the subsequent oxidized additions being such as to afford a continuous oxidation of silicon and carbon contained in the unrefined metal by the oxygen carried by the said consecutive additions.

HORACE WV. LAS H.

itnesses:

JOHN GEORGE SHARP, CHARLES N. FISCUS. 

